Quite some time ago now I set about modifying my Wing Dragon to see how long it could be made to fly for.
Eventually, although keeping to exactly the same dimensions and layout, I ended up with this all new build.
It is built almost entirely from 3mm Depron and weighs just 7oz ready to go less the battery.
It is designed around a 7.5oz 5000mAh 2s which completely fills the nose.
The target was a 'no lift' flight of 2 hours.
Yesterday was calm and rather misty so I had a go.
Launched at 9:56am
Landed at 12:01pm2 Hours 5 minutesNot bad for 40" pusher foamy!

The motor ran the entire time and there was definitely no lift.
As far as I can tell it was not at the LVC but I was about at the limit of my endurance and couldn't face carrying on any longer. I still have a stiff neck!

I think there are a few aerodynamic 'tweeks' possible to increase the duration further but such long flights are difficult and incredibly boring to do. I think I will have to use a much smaller battery and ballast.

For example a 36 minute flight from a 1000mAh battery but ballasted to the weight of a 5000mAh one would be the equivalent to a 3 hour duration.

The next step, a 1000mAh 'ballast' battery.
The same dimensions, weight and weight distribution as the 5000MAh.
The first task is to see how long it will fly with this (about 25 minutes) and then see if I can improve on it, with an ultimate target of 36 minutes.

Flew the Endurance again this afternoon with the 1000mAh ballast battery right down the LVC. It was not really the result I was expecting as it flew for no less than 38 minutes.

All things being equal that would mean the 5000mAh battery would give an absolute endurance of 5x38 = 190 minutes or just over 3 hours and that's before adopting any of the aerodynamic improvements I have in mind.
Perhaps I should be considering a 4 hour target!

Even with its slow speed it could still cover quite a distance.
Maybe a foamy cross channel flight?

this will requie a few drinks,food,maybe a bathroom break. also a tv to glance at watching football[jk].

i really like reading your thread on this subject of endurance flights. may have to give it ago some time. longest flight i'v had so far is aroun 40 mins soaring the skimmer,and my neck was hurting is the only reason i came down. plus i wanted to get off the flight line while other buds were flying.but for the hr+ long flights i'd want a reclining beach chair with head cushion and drink holder. now that would be cool to try.

by the way,the reason for the fast boat on the cross channel fight is so you can hit a pub while the auto pilot gps gyro flys your plane at 10mph across the channel and you step outside to land it when she arrives.

narrow is the place to land...wide is the space to crash....choose the narrow way!

Calm and cold, very cold, this morning.
With the 1000mAh ballast battery on board launched at 8:52. Landed at 9:53.

The maths suggest that with the full 5000mAh the maximum duration is not 4 hours but 5!

Unless the battery is considerably under rated (unlikely) flying for 1 hour on 1000mAh means 1A and with a 2s that's just 7.5W and the radio and servos take some of that as well.
The Endurance weighs 14.5oz so it is using only 8.3W/lb

The Endurance has always flown with a slight off set to the ailerons. I put it down to a small aerodynamic discrepancy in the wing.

I just happened to hold the Endurance up to the light and noticed that the inner pair of wing ribs were not equally spaced from the fuselage centre line but they all appeared equally spaced out along the wing.
It was almost as if the wing was not in the middle........surely not!
Oh yes it is. About 5mm off set!!!
Although it doesn't seem to bother it much.
Centring the wing would be quite involved as the motor would have to be repositioned as well.
Simplest solution shorten the longer wing by cutting off the complete tip, removing 5mm from the centre section and gluing back together.
As the tips were only glued and taped originally no strength will be lost and perhaps not having to off set the ailerons will reduce the drag just a bit.

Just a final update
With the wings now of exactly equal length I tested it today in cold but surprising choppy wind conditions.
It still needed a slight aileron off set so it looks like the wing does have a bit of an aerodynamic twist after all but not a rigorous test as the Endurance does not like any wind at all!

A bit of an update on the Endurance.
Not that I have actually flown for 5 hours or attempted anything like it.

Before I built the Endurance I built a plane that carried its batteries inside the wing box spar.
This allowed the fuselage to be reduced to the diameter of the motor. After a long series of development to overcome all sorts of stability issues it end up looking like this.
It now flies well enough but it still not a 'nice' plane to fly.

The 4 original LiFe cells (3V 1000mAh) were arranged in a 2s2p arrangement.
I recently purchased 4 similar sized Li-ion cells (3.7V 3000mAh).
Of course these cells are not rated much above 1C but this 'minimum' aeroplane only draws 9A at full power and cruises on much less.

The bit I found interesting is that the Li-ion cells are, for a similar capacity, quite a bit lighter (although more bulky) than a LiPo.

The 5000mAh 2s LiPo I use in the Endurance weighs 7.4oz (210g). That weight in Li-ion cells would have a rated capacity of no less than 9000mAh (2s3p).
And remember it can maintain height on just 1A so (in theory) 9 hours!

These are really exceptional results. It shows just how important building light is when it comes to duration.

I cant help thinking that you could get even longer duration if you used a tractor prop configuration which would allow a larger slower turning (and so more efficient) prop. You might also try more pitch on the prop, that may increase cruise efficiency a little more.

These are really exceptional results. It shows just how important building light is when it comes to duration.

I cant help thinking that you could get even longer duration if you used a tractor prop configuration which would allow a larger slower turning (and so more efficient) prop. You might also try more pitch on the prop, that may increase cruise efficiency a little more.

I believe he did change the pitch of the prop at one point, and increased his endurance.

I believe he did change the pitch of the prop at one point, and increased his endurance.

Yes, it made a big difference, but it's still a relatively low pitch prop (8x4.3). The fact that it made such a big difference tends to point to there being more improvement available by going a little further in that direction. I'm pretty sure an 8x6 will give more efficient cruise flight. Worth a try?